Partial denture with movable-arm clasp and method of making the same



Apnl 8, 1969 v. .1. 0000, JR 3,

PARTIAL DENTURE WITH MOVABLE'ARM CLASP AND METHOD OF MAKING THE SAME Filed Sept. 15, 1967 INVENTOR. VINCE NT J. ODDQJR 3,436,825 PARTIAL DENTURE WITH MOVABLE-ARM CLASP AND METHOD OF MAKING THE SAME Vincent J. 041110, in, 161 Bretton Woods Drive, Cranston, RI. 02910 Filed Sept. 15, 1967, Ser. No. 731,664 Int. Cl. A61c 13/22 US. Cl. 32-5 6 Claims ABSTRACT OF TEE DISCLOSURE A partial denture having a movable-arm clasp for complete passivity. There are no springs or spring tensions. A preformed metal housing is molded into a side of the partial. A plastic pattern forms the pivotal base of the movable-arm designed to pivot in the housing. The balance of the arm is formed with wax in the usual manner. The arm is then cast in one piece. The arm pivots in the housing and engages the undercut region of the tooth without ten- SlOl'l.

Background of the invention My present invention relates to partial dentures and more particularly to the type usin a movable-arm clasp which permits insertion, removal and retention with complete passivity and without spring strains.

The present application constitutes an improvement over by Patent No. 3,267,574, issued Aug. 23, 1966, and entitled, Partial Denture With Movable Retaining Arm. Most conventional dentures in use today employ the principle of the lever or a variation thereof in the form of clasps designed to exert forces on the abutting teeth. Attempts have been made to lessen these forces because the continuous application even of a small force results in the loosening of these teeth. It has been found that as long as the frictional engagement offers any resistance, there is a harmful force exerted on the abutting teeth.

The partial denture is faced with the problem of providing support for the denture, a bracing action for the denture, and a retention force to hold it in the mouth. The clasp which has been designed for this purpose exerts a spring tension or pressure on the abutting teeth which, over a period of time, causes the teeth to loosen.

Summary f the invention The principal object of the present invention is therefore to provide a partial denture construction utilizing a retention device which will not exert any pressure against the abutting teeth and will allow a moderate amount of working movement in all directions.

Another object of the present invention is to provide a partial denture having a movable-arm clasp which can be opened for insertion of the denture, then locked in the undercut region of the abutting teeth for retention.

A further object of the present invention is therefore to provide a partial denture having a movable-arm clasp which can be retained in place with complete passivity and without strain.

Another object of the present invention is to provide a novel partial denture with a movable-arm clasp having a novel method of manufacture which renders it quick, easy and simple to fit to the patients mouth.

With the above and other objects and advantageous fea tures in view, my invention consists of a novel arrangement of parts and a novel method of manufacture, more fully disclosed in the detailed description following, in conjunction with the accompanying drawings, and more particularly defined in the appended claims.

Brief description of the drawings FIG. 1 is an enlarged perspective view illustrating the 3,436,825 Patented Apr. 8, 1969 initial steps in the method of manufacturing the partial dentures of the present invention.

FIG. 2 is an enlarged perspective view of the retention arm pivoted in its housing.

FIG. 3 is an enlarged perspective View of the housing.

FIG. 4 is an enlarged perspective view of the plastic pattern for the pivot arm.

FIG. 5 is an enlarged perspective View of a finished clasp in position on a partial.

FIG. 6 is a front view of another form of my invention.

Description 0 the preferred embodiments In my patent hereinabove referred to I disclose the use of a partial denture having a movable retaining arm. In the construction shown therein it was preferably mounted on the inside of the mouth. The housing and pivot arm construction was quite complex and in a single unit, the extended portion of the pivot arm was molded on to the metal base. I have found in practical use that such a construction has certain defects making it diflicult to install, although it does perform its intended function. The present invention is designed to provide a construction much easier to wax up because it is applied to the outside surfaces of the teeth. Furthermore, the present invention utilizes a rigid plastic pattern for the pivot portion of the arm. This merges with the wax portion so that the finished cast piece is a one piece arm having the proper contour for its pivotal end.

Referring more in detail to the drawings illustrating my invention, FIG. 1 illustrates the initial steps taken in the preparation of the construction of the present invention. In the employment of the special housin and pivot member of the present invention certain techniques are required to be practiced by the dentist to accomplish the desired results with a finished product.

The first step is the preparation of a master model Without Waxing out any undercuts on the buccal surface of the teeth to be clasped. This is important because it is these undercut portions that are engaged by the movablearm of the present invention.

Two thicknesses of wax are then placed over the buccal flanges of the edentulous areas. Only one thickness of wax is placed adjacent to the abutment teeth to be clasped. Care must be taken to extend the Wax over the gingival crest to afford proper relief. Now the model is duplicated and the casting investment is poured.

Now referring to FIG. 1, the plastic patterns for the pivotal end of the arms are placed on the model with their flat surfaces against the model and the pivot ends extending towards the center of the area. As can be seen in FIG. 4, each plastic pattern comprises an elongated rectangular portion 10 terminating at one end with an enlarged cylindrical pivot portion 11 having pivot pin portions 12 extending in axial alignment at each end. Note that the cylindrical portion 11 is located towards one side of the portion 10 so that one complete side of the portion 10 is fiat and will lie flat against the model. The portion 10 is also provided at the side opposite the flat side with a vertical rib or ridge 13 extending above and below the level of the portion in to provide upper and lower detents 14 extending from the upper and lower surfaces of the portion 10.

Now referring again to FIG. 1, the model 15 is provided with the edentulous portion 16 where the rigid plastic patterns 17 and 18 are positioned, the patterns 17 and 18 being identical to the pattern hereinabove described in FIG. 4. If the portion 16 is extremely narrow, so that there is insufficient room for the patterns 17 and 18 in horizontal alignment, then they can be Vertically spaced from each other so that they overlap.

Now beginning from the free end of each plastic pattern 17 and 18, a wax arm is continued, such as the arm 19 extending from the pattern 17, and the arm 20 extending from the pattern 18. In the illustrated form the arm 19 is run upwardly into the interproximal space as far as possible to take advantage of the undercut area. Note that in this form the arm 19 is provided with two additional wings 21 in an arrow shape which will hug the undercut portion of the abutting teeth. In the form illustrated at the arm 20, this terminates in an arcuate portion 22 extending well under the undercut portion of the abutting tooth. Either or both forms can be used to suit the different situations.

After investing and casting, the resultant arm will be in a single piece as illustrated in FIGS. 2 and 5. In this form the arm 20 is shown with an arcuate portion 23 extending from a single integral arm 2 having the upper and lower detent section 25, a cylindrical pivot section 26, and upper and lower pivot pins 27 integral with the section 26.

The lock housing for pivoting and receiving the movable-arm is illustrated in FIGS. 2 and 3. Referring to FIG. 3, the housing comprises a small narrow rectangular metal housing having a vertical solid rear wall 28, from which a top wall 29, and a bottom wall 30, extend horizontally in spaced parallel relation. In view of the fact that there are no front or side walls, the walls 29 and 30 provide a resilient lock action therebetween. The walls 29 and 30 are provided with spaced slots 31 which extend inwardly from the front free edges thereof to divide each wall portion into three resilient sections. As can be seen in FIG. 2, this permits the cylindrical portion 26, with the upper and lower pivot pins 27, to be inserted into the central section which will spread the portions intermediate the slots 31 and permit the pivot pins to snap into pivot openings 32 therein. All this is accomplished without disturbing the outer sections. Now the outer sections are provided with depressions 33 extending into each wall portion 29 and 30 from the inside outwardly. Now referring again to FIG. 2, when the arm 24 is pivoted on its pin 27 in the opening 32 to the right, then the detent portion will separate the portions 29 and with a resilient action until it reaches the depressions 33, it will then snap into place to releasably retain the arm in that position.

Now referring to FIG. 5, the housing shown in FIG. 3 is molded into edentate portion 16 with the pivot end of the arm 24 already inserted as hereinabove described. Now in this form it is provided that the arm will swing to the left. In which case the portion of the housing to the right is filled with the acrylic plastic as it is not needed. In the form illustrated in FIG. 5, the end of the arm is provided with an arcuate portion 34 which engages the undercut portion of the abutting tooth 35, and the arm is provided with a downwardly extending loop portion 36 to take care of a cramped space. This illustrates the versatility of what can be accomplished with the structure of the present invention. By the same token the arm can be extended to the next abutting teeth if desired.

The above method therefore provides an open faced small resilient lock housing which can be molded into the base of the partial construction and provided with a unitary one piece integral arm which has been formed to fit the patients tooth. Furthermore, by grasping and engaging the teeth down in the undercut portion near the gingival line, the structure remains virtually unseen and unnoticed. The partial is braced and retained in place without pressure on the abutting teeth. To remove the partial it is merely necessary to swing the arms into open position against the action of the detents and resilient action of the housing. After removing or placing it in position it is a simple matter to snap the arms back into position.

The construction of the present invention provides for the elimination of spring tension from the clasp arms at all times. Each clasp is treated separately and a common path of insertion of a number of clamps on one partial denture is no longer of any concern. Clasp tension, loosening, flexibility, and breakage are no longer a factor since passivity eliminates the stress and flexibility.

The above mentioned principle of a hinge-action or movable-arm can also be used in the construction of removable-fixed bridgework whereby the integral one piece arm can be already formed in a metallic material such as gold or stainless steel. As illustrated in FIG. 6, the preformed arm 37 is molded in the removable section of the bridgework, and a preformed slot 38 is made in the crown of the patients tooth. To remove the bridge, it is merely necessary to swing the arm 37 on the bridge 39 out of the slot in the crown of the patients tooth 40. After removal, it is a simple matter to snap the arm 37 back into the preformed recess 38 in the patients tooth 40 to lock the bridge 39 back into position in the mouth.

This construction allows each lock to be treated separately without a common path of insertion, as each lock on both sides of the bridge is treated separately with its individual preformed movable-arm. Other advantages of the present invention will be readily apparent to a person skilled in the art.

1 claim:

1. A denture including a plastic base for mounting an artificial tooth thereon, and means for releasably locking said denture to the adjacent natural teeth, said locking means comprising a pair of housings imbedded in the outside side portion of said denture, an integral one piece arm pivotally mounted in each of said housings, the free end of one arm fitting under the undercut portion of the adjacent teeth on one side and the free end of the other arm fitting under the undercut portion of the adjacent teeth on the other side when said arms are pivoted along said housings against said teeth, and means in said housing for releasably engaging said arms in locking position, each of said housings comprising a pair of horizontally spaced parallel rectangular upper and lower wall portions integrally connected by a single rear vertical wall portion, said upper and lower portions having aligned pivot openings for receiving the pivot end of said arm.

2. A denture as in claim 1, wherein said housings are provided with recesses and said arms are provided with detents for snapping into said recesses to releasa'bly lock said arms in position against said teeth.

3. A denture as in claim 1, wherein said housings are provided with spring sections for retaining said arms in pivoted relation.

4. A denture as in claim 1, wherein said upper and lower Wall portions are provided with spaced parallel slots to provide a spring action at said aligned pivot openings.

5. A denture as in claim 2, wherein said housings are provided with spring sections for retaining said arms in pivoted relation.

6. A denture as in claim 1, wherein said adjacent teeth are provided with a recessed cap, the free ends of said arms entering said recesses to form a fixed-removable bridge.

References Cited UNITED STATES PATENTS 1,526,129 2/1925 Fortunati 32-5 1,673,286 6/1928 Inoque 32S 1,953,715 4/1934 Joife 325 ROBERT PESHOCK, Primary Examiner. 

